OpenAtom is a highly scalable and portable parallel program for molecular dynamics simulations at the quantum level. It implements the Car-Parrinello ab-initio Molecular Dynamics (CPAIMD) method. OpenAtom is written using the Charm++ parallel programming framework. It runs on a variety of architectures like PowerPC, Opteron and Intel-based systems. OpenAtom has shown efficient scaling upto 20,480 processors of Blue Gene/L, 8,192 processors of Blue Gene/P and 4,096 processors of Cray XT3. It runs well on various teragrid systems like NCSA's Cobalt (SGI Altix) and Abe (Dell), TACC's Lonestar (Dell) and Ranger (Opteron), CSE's Turing (Apple) and others.